Method of earth wall construction using cementitious bentonitic mud

ABSTRACT

A method of constructing a fluid impermeable wall in the ground. A first trench is dug and simultaneously filled with a cementitious bentonitic mud, which is sufficiently viscous to prevent the sides of the trench from caving in. This first trench forms a first section of the wall. Before the mud of the firt section has set, a second trench is dug adjacent to and continuing or extending from the first trench, to form a second wall section, and the second trench is also simultaneously filled with cementitious bentonitic mud. The abuttting end sections then bond firmly together upon setting to form a continuous wall.

United States Patent Caron et al.

[ METHOD OF EARTH WALL CONSTRUCTION USING CEMENTITIOUS BENTONITIC MUD [75] Inventors: Claude Caron, Samoreau; Jean Hurtado, Paris, both of France [73] Assignee: Soletanche Societe Auonyme, Paris,

France [22] Filed: June 15, 1971 211 App]. No.2 153,424

[30] Foreign Application Priority Data June 16, 1970 France 7022l0| [52] US. Cl. 61/35, 61/39 [51] Int. Cl E02d 5/18 [58] Field of Search 61/35, 36, 30, 39

[56] References Cited UNITED STATES PATENTS 3,310,952 3/1967 Veder 61/35 2,791,886 5/1957 Veder 61/35 X Sept. 18, 1973 3,464,665 9/1969 Schoewert 61/35 X 3,603,099 9/1971 Zakiewicz 61/35 X 3,422,627 1/1969 Courte 61/35 3,645,101 2/1972 Sherard 61/35 Primary Examiner-Mervin Stein Assistant Examiner--Philip C. Kanman Attorney-Richard C. Sughrue et al.

[57] ABSTRACT A method of constructing a fluid impermeable wall in the ground. A first trench is dug and simultaneously filled with a cementitious bentonitic mud, which is sufficiently viscous to prevent the sides of the trench from caving in. This first trench forms a first section of the wall. Before the mud of the firt section has set, a second trench is dug adjacent to and continuing or extending from the first trench, to form a second wall section, and the second trench is also simultaneously filled with cementitious bentonitic mud. The abuttting end sections then bond firmly together upon setting to form a continuous wall.

11 Claims, No Drawings METHOD OF EARTH WALL CONSTRUCTION USING CEMENTITIOUS BENTONITIC MUD One method of constructing a fluid permeable dia phragm wall in the ground consists of digging a trench in the ground and maintaining the trench full of a ben tonitic mud, which is sufficiently viscous or thixotropic to prevent the earth walls of the trench caving in, whilst the digging is carried out through the mud. The mud is subsequently displaced by concrete to form the finished wall in situ in the ground. This method has the disadvantage that the long diaphragm wall has to be constructed in longitudinally displaced sections and some form of fluid tight seal, and in many cases also a mechanical connection, has to be made between the adjacent ends of the adjacent sections. Also there is a difficulty of storing, carting, recovering and regenerating the bentonitic mud when each section is cast.

In accordance with the present invention in a method of constructing in the ground a fluid impermeable diaphragm wall incorporating a number of longitudinally displaced sections, each wall section consists of a length of trench filled with cementitious bentonitic mud and of each two adjacent sections one is first constructed and the other one is then constructed before the mud of the first section has set so that the mud in the two sections bond together to provide a perfect fluid impermeable diaphragm wall. Such a wall is thus produced without having to insert or construct a fluid tight seal between the two sections.

The use of a bentonitic mud which includes a proportion of cement surprisingly retains the high viscous or thixotropic properties of bentonitic mud as well as the setting properties of cement.

Numerous tests by the applicants have proved that slow setting cementitious bentonitic mud makes it possible to cast slabs, constituting separate wall sections, of which the ends of the slabs have set sufficiently after 24 to 48 hours to tolerate the absence of pressure of the soil during the forming of an adjacent slab section, but insufficiently to provide any difficulty of uniting with the adjacent section when it is cast. Experiments have shown that the same results are obtained whatever the type of cement employed, provided that the setting speed is adjusted as necessary by adding to the cementitious bentonitic mud an appropriate retarding agent.

Preferably if the setting time of the mud-is T, the second one of the two sections is constructed in a period between 0.5 T and 0.9 T after the first one of the sections has been constructed. A typical diaphragm wall may have a thickness of between 0.2 and l m and a depth of between 1 and 60 m.

The manner in which the diaphragm wall is constructed of separate sections is open to many variations. Thus a first-section may be constructed, then the next section but one, and finally the intermediate section before the first two sections have set fully. It is then preferable if the partially set inner ends of the end sections are cut off during the construction of the middle section to ensure that no earth remains to interfere with the seal between the adjacent sections. Again it is possible to work simultaneously at several sections, using several machines, or to work progressively along the wall section by section.

A diaphragm wall of exceptionable permeability, even to gases, can be produced by embedding into the wall sections a continuous foil of plastics material extending along the wall. Alternatively if exceptional strength is required, metal reinforcement may be embedded in the sections. In either case the plastic sheeting or reinforcement is simply immersed in the mud filled trench and remains there until the mud has set.

The invention thus makes possible the construction of a diaphragm wall of indefinite length, or a circular or other endless diaphragm wall, as an integral fluid tight unit without the need for any additional jointing material. The wall also has the property of being slightly flexible so that it can move slightly with the ground without impairing its impermeability. Since the mud forms the finished wall sections it does not have to be recovered and forms a cheap building material for the wall.

By way of example the invention may be carried out using a cementitious bentonitic mud consisting of bentonite containing a quantity of between 50 and 300 kilograms of cement per cubic metre. The proportion is preferably between 50 and kilograms per cubic metre for particularly impermeable walls and between 100 and 300 kilograms per cubic metre when greater strength is required. The mud should retain a substantially constant high viscosity for at least 40 hours and remain homogeneous for that period. This period can be reduced if the speed with which the work is carried out so requires, but whatever the setting time, it is preferably selected so that the cement and bentonite mixture with which the or each trench is filled, retains its homogenity and viscosity until all the construction steps have been completed.

lt is obvious that, by reason of the very numerous types of cement available, there is a very vast variety of mixtures for fulfillingfthese conditions. Appropriate retarding agents may be incorporated as necessary.

In the case of a fine cement obtained by a mixture of clinker and slag from blast furnaces, the amount of retarding agent used depends upon the proportion of clinker, whereas when the cement is made without clinker that is to say from substantially pure slag, no retarding agents are necessary.

Conversely, if for any reason that at any stage, it is desired to accelerate the setting of the whole or part of the cementitious bentonitic mud, it is only necessary to add to the mud already in place. a certain quantity of setting accelerator, for example cement without slag.

What we claim is: l. A method of constructing in the ground a fluid impermeable diaphragm wall composed of a plurality of longitudinally extending sections bonded together to form a wall, said method comprising:

excavating a first section and simultaneously completely filling the excavation with a cementitious mixture consisting essentially of bentonitic mud and cement; before said cementitious mixture in the excavated first section completely hardens and sets, excavating a second section adjacent said first section while simultaneously completely filling in the excavation of said second section with said cementitious mixture; and allowing the mixtures filling the excavation of each of said sections to harden therein whereby when the mixtures in each of said sections harden they bond together at the junction of said first and said second sections to thereby provide a fluid impermeable wall'consisting essentially of said hardened cementitious mixture.

2. A method according to claim 1, in which of three consecutive sections along the wall, the end sections are first constructed and the middle section is then constructed before the mud of the end sections has set.

3. A method according to claim 2, in which the partially set inner ends of the end sections are cut off during the construction of the middle section to ensure that no earth remains to interfere with the seal between the adjacent sections.

4. A method according to, claim 1 wherein the setting time of the cementitious mixture is T and the second one of the two sections is constructed in a period between 0.5 T and 0.9 T after the first one of the sections has been cast.

5. A method according, claim 1 wherein the diaphragm wall has a thickness of between 0.2 and l m and a depth of between 1 and 60 m.

6. A method according to, claim 1 in which a continuous foil of plastics material, extending along the wall, is embedded in the sections.

7. A method according to, claim 1 in which metal reinforcement is embedded in the sections.

8. A method according to, claim 1 in which the cementitious mixture consists essentially of bentonite mud and from 50 to 300 kilograms of cement per cubic metre.

9. A method according to, claim 1 in which a retarding agent is present in the mixture to render the mixture more slowly setting.

10. A method of constructing in the ground a fluid impermeable diaphragm wall composed of a plurality of longitudinally extending sections bended together to form a continuous wall, said method comprising:

a. excavating a first section and simultaneously completely filling the excavation with a cementitious mixture consisting of bentonitic mud and from 50 to 300 kilograms of cement per cubic meter of mixture,

b. before said cementitious mixture completely filling the excavated first section completely hardens and sets, excavating a second section adjacent said first section while simultaneously completely filling the excavation of said second section with said cementitious mixture,

c. allowing the mixtures filling the excavations of each of said sections to harden therein, and

d. repeating step (a) (0) until a wall of the desired length is obtained, whereby when the mixtures in each of said sections harden they bond together at the junction with each adjacent section to thereby provide a continuous fluid impermeable wall consisting of said hardened cementitious mixture.

11. A method of constructing in the ground a fluidimpermeable diaphragm wall composed of a plurality of longitudinally-extending sections bonded together to form a continuous wall, said method comprising:

1. excavating a first section and simultaneously completely filling the excavation with a cementitious mixture consisting of bentonitic mud, from 50 to 300 kilograms of cement per cubic meter of said cementitious mixture and a retarding agent to render the cementitious mixture more slowly setting;

2. before said cementitious mixture completely filling the first excavated first section completely hardens and sets, excavating a second section adjacent said first section while simultaneously completely filling the excavation of said second section with said cementitious mixture;

3. allowing the mixtures filling the excavations of each of said sections to harden therein; and

4. repeating steps (l)- (3) until a wall of the desired length is obtained, whereby when the cementitious mixtures in each of said sections harden they bond together at the junction with each adjacent section to thereby provide a continuous fluid impermeable wall consisting of said hardened cementitious mixture. 

1. A method of constructing in the ground a fluid impermeable diaphragm wall composed of a plurality of longitudinally extending sections bonded together to form a wall, said method comprising: excavating a first section and simultaneously completely filling the excavation with a cementitious mixture consisting essentially of bentonitic mud and cement; before said cementitious mixture in the excavated first section completely hardens and sets, excavating a second section adjacent said first section while simultaneously completely filling in the excavation of said second section with said cementitious mixture; and allowing the mixtures filling the excavation of each of said sections to harden therein whereby when the mixtures in each of said sections harden they bond together at the junction of saiD first and said second sections to thereby provide a fluid impermeable wall consisting essentially of said hardened cementitious mixture.
 2. A method according to claim 1, in which of three consecutive sections along the wall, the end sections are first constructed and the middle section is then constructed before the mud of the end sections has set.
 2. before said cementitious mixture completely filling the first excavated first section completely hardens and sets, excavating a second section adjacent said first section while simultaneously completely filling the excavation of said second section with said cementitious mixture;
 3. allowing the mixtures filling the excavations of each of said sections to harden therein; and
 3. A method according to claim 2, in which the partially set inner ends of the end sections are cut off during the construction of the middle section to ensure that no earth remains to interfere with the seal between the adjacent sections.
 4. A method according to, claim 1 wherein the setting time of the cementitious mixture is T and the second one of the two sections is constructed in a period between 0.5 T and 0.9 T after the first one of the sections has been cast.
 4. repeating steps (1) - (3) until a wall of the desired length is obtained, whereby when the cementitious mixtures in each of said sections harden they bond together at the junction with each adjacent section to thereby provide a continuous fluid impermeable wall consisting of said hardened cementitious mixture.
 5. A method according, claim 1 wherein the diaphragm wall has a thickness of between 0.2 and 1 m and a depth of between 1 and 60 m.
 6. A method according to, claim 1 in which a continuous foil of plastics material, extending along the wall, is embedded in the sections.
 7. A method according to, claim 1 in which metal reinforcement is embedded in the sections.
 8. A method according to, claim 1 in which the cementitious mixture consists essentially of bentonite mud and from 50 to 300 kilograms of cement per cubic metre.
 9. A method according to, claim 1 in which a retarding agent is present in the mixture to render the mixture more slowly setting.
 10. A method of constructing in the ground a fluid impermeable diaphragm wall composed of a plurality of longitudinally extending sections bended together to form a continuous wall, said method comprising: a. excavating a first section and simultaneously completely filling the excavation with a cementitious mixture consisting of bentonitic mud and from 50 to 300 kilograms of cement per cubic meter of mixture, b. before said cementitious mixture completely filling the excavated first section completely hardens and sets, excavating a second section adjacent said first section while simultaneously completely filling the excavation of said second section with said cementitious mixture, c. allowing the mixtures filling the excavations of each of said sections to harden therein, and d. repeating step (a) - (c) until a wall of the desired length is obtained, whereby when the mixtures in each of said sections harden they bond together at the junction with each adjacent section to thereby provide a continuous fluid impermeable wall consisting of said hardened cementitious mixture.
 11. A method of constructing in the ground a fluid-impermeable diaphragm wall composed of a plurality of longitudinally-extending sections bonded together to form a continuous wall, said method comprising: 